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Re: sparsemem support on MIPS

To: naveen yadav <yad.naveen@gmail.com>
Subject: Re: sparsemem support on MIPS
From: David VomLehn <dvomlehn@cisco.com>
Date: Thu, 19 Aug 2010 16:06:14 -0700
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Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, sshtylyov@mvista.com, Michael Sundius <msundius@cisco.com>
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On Thu, Aug 19, 2010 at 09:04:21PM +0530, naveen yadav wrote:
> 
>  Dear all,
> 
> I build MIPS 32 with sparsemem support to take care of holes in
> physical memory, this conserve memory but put overhead to speed
> because of pointer redirection in pfn_to_page().
> 
> To prevent this conversion I tried to use
> CONFIG_SPARSEMEM_VMEMMAP_ENABLE on MIPS 32 but kernel build fails
> becauase most of the supported functions related to vmemmap are
> supported for 64 bit architectures only.
> 
> I wish to compare memory and speed result with / without
> CONFIG_SPARSEMEM_VMEMMAP_ENABLE in MIPS 32. I need your comment in it
> ?

We use sparse memory and submitted a patch some while ago to add support,
but it died for lack of interest. The patch was relative to a kernel
from several released ago; I don't know whether it would apply to
the tip. I can see if I track it down.
-- 
David VL

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